1. Field of the Invention
The present invention relates to a tire tread rubber composition with excellent wear resistance and low fuel consumption.
2. Related Art Statement
In order to assure fuel saving of a tread rubber of tires, particularly tires for use in large scaled vehicles, the following measures have been heretofore adopted:
(a) Styrene butadiene rubber (SBR) is inappropriate, and natural rubber (NR) and butadiene rubber (BR) are most suitable. Therefore, the latter rubbers are used.
(b) Carbon black is replaced by low reinforcing carbon black.
(c) A compounding addition amount of carbon black is reduced.
On the other hand, in order to improve the wear resistance, the following measures have been adopted.
(a') The compounding amount of the carbon black is increased.
(b') Carbon black is replaced by high reinforcing carbon black with a high specific surface area.
(c') NR and BR are used as rubber component.
However, the wear resistance is deteriorated by adopting the above fuel saving-assuring measures (a) and (b). On the other hand, by using too much BR in the rubber components in the wear resistance-improving measures, the wear resistance is also lowered. Therefore, it is necessary to use natural rubber in an amount of not less than 50% by weight. Further, the fuel saving-assuring is deteriorated in the case of the counter-measures (a') and (b'). As mentioned above, the fuel saving-assuring measures and the wear resistance-increasing measures exhibit the opposed tendencies in the conventional techniques, and it has been impossible to attain both characteristics. Thus, it has a long felt desire to develop the tread rubber compositions suitable for tire tread rubber with both the performances, particularly the tread rubber of pneumatic tires for use in large scaled vehicles such as trucks, buses, etc.